The February 1974 Staff Report of the National Industrial Pollution Control Council (U.S. Government Printing Office 1971, 431-795/200) on the subject of "Animal Wastes" summarized the growing problem of pollution of water, soil and air resources created by the waste products of farm animals. A major source of environmental pollution is the excreted waste products of farm animals in feedlots, particularly beef cattle. More specific information has been published in "The Mounting Problem of Cattle Feedlot Pollution," Agricultural Science Review, U.S. Department of Agriculture, Volume 9, No. 1, 1971.
In a paper "A Systems Approach to Cattle Feedlot Pollution Control" presented at the May 1972 National Meeting of the American Institute of Chemical Engineers, St. Louis, Mo., Dr. Eugene Coleman analyzed the manure slurry discharged from a slotted floor confinement feedlot, in which the manure accumulates in subfloor pits cleaned out periodically by cable drawn scraper blades. The daily discharge from a feedlot with 10,000 head of average 800 pound cattle is a slurry containing about 45 tons (dry weight) of solids in about 70,000 gallons of water plus additional water from overflow of watering troughs and from rainstorm runoff. Each such 10,000 head feedlot module creates the quivalent of the sewage pollution potential of a city of 100,000 persons. Feedlot installations for 50,000 head or more are not unusual.
U.S. Pat. No. 3,859,962 granted to Ralph Kissinger, Jr., describes an improved flushable feedlot floor including multiple inclined floor slabs sloped to drain manure into subfloor slotted flumes which are cleaned by hydraulic flushing. In cold weather areas, such feedlots are usually flushed with manure liquid effluent recirculated from a storage lagoon which in turn is emptied occasionally for disposal on agricultural lands.
As regards energy and feed utilization, most cattle feeding operations are relatively inefficient. Typically each head of cattle consumes a daily ration of about 20 pounds of high quality feed, including highcost cereal grains plus about 5 gallons of water, to produce a daily marketable weight gain of about 2-1/2 pounds plus about 65 pounds of manure slurry. Much of the organic nutrient potential of the feed is not assimilated by the animals and is discharged as a partially digested biologically active manure slurry with major environmental pollution potentials if discharged to surface or subsurface waters, or if allowed to decompose and volatilize on exposure to sun and air. If stored in lagoons, anaerobic decomposition will convert the material to a relatively worthless sludge plus gases dissipated to the atmosphere.
Raw manures from farm animals are often used as fertilizer for distribution to agricultural lands. However, its value for direct use is limited by the fact that such material is only partly decomposed. In the soil, aerobic bacterial decomposition of the more volatile organic nutrients proceeds very rapidly and in this process the microorganisms utilize nitrogen that would otherwise be available for stimulation of fieldcrop growth. Such nutrients are returned to the soil eventually upon eventual decomposition of the manure; however, the short term fieldcrop growth results may be unsatisfactory.
In the co-pending patent application of Lennart G. Erickson and Wm. Scott Erickson, "Microorganic Fertilizer Manufacturing Method," Serial 528,070, there is described an improved biochemical method for use of the volatile organic fraction of farm animal manure as raw materials for manufacture of an improved liquid fertilizer. This continuous processing method for year-round production and distribution of liquid fertilizer is of limited utility in areas where extended periods of below freezing weather occur. The quantity of fertilizer produced is such that economical use of this method is restricted to situations where large areas of nearby agricultural lands are available for efficient utilization.